Wheel chair shock absorber



July 2l, 1959 F. H. JoHNsoN WHEEL CHAIR SHOCK ABSORBER Filed June 14,1954 United States Patent WHEEL CHAIR SHOCK ABSORBER Franklyn H.Johnson, deceased, late of 'Los Angeles, Calif., by Robbie F. Johnson,executrix, Fresno, Calif.

Application June 14, 1954, Serial No. 436,452

3 Claims. (Cl. 280-124) My invention relates to shock absorbers, and itrelates particularly to a shock absorber for a wheel chair or the like.

It is well known in the art to provide spring suspension means forincreasing the riding comfort of the Wheel chairs.

However, it has long been a problem in the art to provide a wheel chairshock absorbing mechanism which does not interfere with the delicatealignment of the wheel chair.

It has also been a problem in the art to provide a wheel chair shockabsorbing mechanism which may be readily applied to an ordinary wheelchair Without substantially altering the structure of the wheel chair.

It is therefore an object of my present invention to provide a wheelchair shock absorber which does not in any way interfere with thealignment of the wheel chair.

It is another object of my present invention to provide a wheel chairshock absorber which may be manufactured separately and installed easilyon an ordinary wheel chair without substantial alteration of the Wheelchair structure, or which may alternatively be produced as a componentpart of the wheel chair when the wheel chair is initially constructed.

Another object of my present invention is to provide a wheel chair shockabsorber which is adjustable for various weights.

A further object of my present invention is to provide a Wheel chairshock absorber adapted to be operatively associated with each rear wheelof a wheel chair, so that a pair of my shock absorbers mounted on awheel chair may be equalized to provide balanced, uniform shockabsorbing qualities to both sides of the wheel chair.

Other objects and advantages of my present invention will be apparentfrom the following description and claims, the novelty of my inventionconsisting in the features of construction, the combinations of parts,the novel relations of the members and the relative proportioning,disposition and operation thereof, all as is more completely describedherein and as is more particularly pointed out in the appended claims.

In the accompanying drawings, forming a part of my presentspecification:

Figure l is a rear elevational view of a standard folding wheel chairemploying my shock absorbers.

Figure 2 is a vertical section taken along the line 2-2 of Figure l.

Figure 3 is a horizontal section taken along the line 3-3 of Figure 2showing further details of my shock absorber.

Referring to my drawings, in Figure 1 I yhave shown a folding wheelchair including vertical side frame posts 12 and 14, flexible chair back16 suspended between frame posts 12 and 14, and rearwardly extendingoperating handles 18 integrally connected to the respective verticalside frame posts 12 and 14 at their upper ends.

A pair of crossed folding braces 20 are pivoted at central pivot 22.

A pair of rearwardly extending, generally horizontal frame legs 24 and26 are integrally connected to the lower ends of vertical side frameposts 12 and 14, respectively, horizontal frame legs 24 and 26facilitating manipulation of the wheel chair by a person who is pushingthe wheel chair.

A pair of my shock absorber units 30 and 32 are operatively connectedwith the main wheels 34 and 36, respectively, of the wheel chair. WhileI have shown my shock absorber units 30 and 32 operatively positioned ona standard folding type of wheel chair, it is to be understood that myshock absorber units may be applied to any standard type of wheel chair.

Referring now to Figures 2 and 3 in which I have illustrated my shockabsorber unit in detail, the wheel axle 38 is fitted into a counterbore40 to be threadedly enga-ged in the thread bore 42 forming acontinuation of counterbore 40, bores 40 and 42 being provided in thebody portion 43 of U-shaped rocker arm 44. An adjustable lock screw 45is threadedly engaged in the end portion of thread bore 42 to permitlocking engagement of axle 38 with rocker arm 44 in a manner whichexposes the proper amount of axle 38 to permit wheel 34 to freely rotateon axle 38.

A pivot pin 46 is pivotally mounted in bearings 48 which are disposed inthe respective leg portions of rocker arm 44. Vertical side frame posts12 and 14 are provided with integral frame bosses 50 having lateralthreaded `bores 52 adapted to receive axles 38 when the wheel chair isused without my shock absorbers. I mount my rocker arm 44 on frame boss50 by placing the leg portions of rocker `arm 44 on opposite ends ofboss 50 and then inserting pivot pin 46 through bearings 48 in the legportions of rocker arm 44 and also through the threaded bore 52 of boss50, the external threads on pivot pin 46 permitting pin 46 to bethreaded into locking engagement in the threaded bore 52 of boss 50.

A set screw 54 is threadedly mounted in one of the legs of U-shapedrocker arm 44 to engage annular groove 56 in one end of pivot pin 46 toprevent any lateral movement of rocker arm 44 with respect to frame boss50.

I provide an ear 58 which extends rearwardly from body portion 43 ofU-shaped rocker arm 44, and ear 58 is pro-vided with an elongatedopening or slot 60 which received the upper end of a rod 62.

Rod 62 is preferably provided in the form of a bolt, the head portion ofwhich extends downwardly below slot 60 into shock absorber cylinder 64.The upper end of shock absorber cylinder 64 is closed, except for avertical passage 65 which is centrally located in the upper end ofcylinder 64 to receive rod 62. A plug 66 having a central bore toreceive rod 62 may be provided in the upper end of cylinder 64 toprevent wear on passage 65 by reciprocation of rod 62, and to provide abase over which the upper end of cylinder 64 may be spun inwardly duringproduction.

A helical compression spring 67 is disposed about rod 62 in shockabsorber cylinder 64, with its upper end in abutment with plug 66 andits lower end abutting against a retainer 68 that is supported on thelower end of rod 62.

A washer 70 having an elongated opening therethrough is mounted on theupper end of rod 62 above ear 58, and a lock nut 72 is threadedlymounted on rod 62 above washer 70. The upper surface of washer 70 is anarcuate or cylindrical surface, the arc being aligned longitudinallywith the wheel chair, and the lower surface of lock nut 72 is a similararcuate or cylindrical surface having a larger diameter. This arcuateconstruction of -the upper surface of washer 70 and the lower surface oflock nut 72 provides a pivotal engaging surface between the shockabsorber unit 30 and the U-shaped rocker arm 44, and also prevents locknut 72 from unscrewing off of the end of rod 62.

If it is desired, a ball and socket type of joint may be providedbetween ear 58 and rod 62 instead of the arcuate washer and lock nutconstruction which I have shown and described.

A plug 76 is provided in the lower end of shock absorber cylinder 64,and is retained in its position by means of a laterally disposed pin 78which extends through cylinder 64. A slot 80 is provided in plug 76 toaccommodate the upper end of a link 82 which is pivotally mounted on pin78, and the lower end of link 82 is pivotally connected, by means of asuitable bolt 84, to tube clamp 86 which is adapted to clamp tightlyabout one of the horizontal frame legs 24 or 26 by tightening of bolt84.

Although my wheel chair shock absorber may be built into a wheel chairwhen the wheel chair is initially constructed, I prefer to provide mywheel chair shock absorber as a separate unit which may be quickly andeasily installed on an ordinary wheel chair. In order to install mywheel chair shock absorber on a standard wheel chair which is producedwithout the shock absorber, al1 that is necessary is to unscrew andremove the axle 38 from the frame boss 50 on each side of the wheelchair and then attach one of my shock absorbers to each side of thewheel chair. The first step in this attachment is to set the rocker arm44 around frame 'boss 50 in the manner shown in Figure 3 and to slippivot pin 46 through bearings `48 in rocker arm 44 and into threadedengagement with the threaded bore inside of frame boss 50, lockingrocker arm 44 against lateral motion with respect to frame boss 50 byengagement of set screw 54 in annular groove 56.

At any convenient time, the same axle 38 which was removed from itsinitial operative engagement with frame boss 50, or a new axle 38 ifdesired, is slipped through the wheel 34 or 36 and is threadedly engagedin thread bore 42 through body portion 43 of rocker arm 44. When axle 38has been threaded into bore 42 the correct amount to provide thenecessary clearance for wheel 34 or 36, the lock screw 45 is tightenedagainst the end of axle 38 to lock axle 38 in this operative position.

Then the upper end of rod 62 which protrudes upwardly from the top ofshock absorber cylinder 64 is moved upwardly through slot 60 in ear 58,washer 70 is slid down onto the top of rod 62 and lock nut 72 is engagedon the upper end of rod 62.

All that remains to complete the installation of my shock absorber onthe wheel chair is to engage tube clamp 86 on horizontal frame leg 24 or26 in the manner shown in Figure 2.

Itis obvious that lthe above installation steps may occur in any desiredorder, the only step being required in any particular order being theremoval of axle 38 from its normal operative engagement in frame boss 50before my shock absorber is installed.

Once my shock absorber is installed, it may be adjusted by theadjustment of lock nut 72 to accommodate persons of dilerent weight,lock nut 72 being moved downwardly on rod 62 for a heavier person, orupwardly on rod 62 for a lighter person. Proper adjustment of my shockabsorber units on each side of the wheel chair in this manner willpermit the shock absorbing action on both sides of the wheel chair to beequalized, so that my shock absorbers do not in any way interfere withthe perfect balance and alignment of the wheel chair.

The weight of the person sitting in the wheel chair is applied to theshock absorber through horizontal frame leg 24 or 26, a sudden downwardjolt of the chair moving frame leg 24 or 26 downwardly to pull theentire shock absorber cylinder 64 downwardly relative to rod 62 which issuspended from the wheel 34 or 36 because of the attachment of both rod62 and wheel axle 38 to rocker arm 44. This causes compression of spring67, thus taking up the shock. Y

As relative movement thus occurs between cylinder 64 and rod 62, atwisting movement will occur between rod 62 and ear 58 of rocker arm 44.'Ihe elongated shaping of slot 60 in ear 58 and washer 70 permits thistwisting movement to occur, and the bearing for accommodating thistwisting action is the curved surface connection between the uppersurface of washer 70 and the lower surface of lock nut 72.

The rotatable mounting of rocker arm 44 on pivot pin 46 permits rockerarm 44, and hence the wheel 34 or 36 to swing freely in an arc aboutpivot pin 46.

Although I have illustrated a shock absorber unit 30 or 32 consisting ofa spring loaded cylinder, in which the wheel chair is supported onspring compression, it is to be understood that any other suitable shockabsorber unit may be substituted for the unit described in detailhereinabove. Thus, a spring tension type of shock absorber unit may beused, or a pneumatic or a hydraulic type of shock absorber unit may beused if it is desired.

Another change which may be made without departing from the spirit of myinvention is the substitution of a ball and socket join for my preferredwasher and lock nut engagement at 74.

My wheel chair shock absorber introduces an entirely new element in thewheel chair suspension art, namely, my U-shaped rocker arm 44 which isadapted to be pivotally mounted on the wheel chair frame boss thatoriginally accommodated the axle, and that is also adapted to suppportthe wheel chair axle in spaced relationship to its original position onthe wheel chair.

Another entirely new element in the Wheel chair suspension art is myadjustable feature which permits the adjustment of my shock absorbers toaccommodate varying weights, and particularly to equalize the shockabsorbers on both sides of the wheel chair so that the perfect alignmentof the wheel chair is not disturbed.

These new elements, together with their new functions and modes ofoperation, produce the surprisingly new results of permitting anordinary wheel chair to be transformed into a wheel chair with shockabsorber mounting swiftly and with very little effort, and also ofpermitting Vaccurate wheel chair alignment and shock absorberadjustment.

Probably the greatest diiculty in connection with prior art wheel chairshock absorbing mechanisms was the alignment problem. I have completelyeliminated this problem not only by my adjusting feature which permitsthe relative adjustment of the shock absorbers on both sides of a wheelchair, but also by my novel axle mounting structure. While my axle 38 ismovably suspended with respect to the wheel chair frame, it is preventedfrom any lateral shifting whatsoever by the pivotal engagement of myU-shaped rocker arm 44 on frame boss 50, and is at all times keptsubstantially parallel to the bore 52 in frame boss 50 by my rocker armmounting.

Another surprisingly new result of my invention is that it displaces thewheels of the wheel chair rearwardly from their original positionsrelative to the wheel chair frame, thus preventing a wheel chairembodying my invention from tipping over backwards.

It is to be understood that the form of my invention herein shown anddescribed is my preferred embodiment and that various changes in theshape, size and arrangement of parts may be resorted to withoutdeparting from the spirit of my invention, or the scope of my appendedclaims.

What is claimed is: j

1. Apparatus for converting a conventional wheel chair of the typehaving a frame with a pair of spaced frame members that havesubstantially horizontal wheel axlereceiving passages therethrough intoa spring supported wheel chair; including a pivot pin engageable in eachof said wheel chair axle-receiving passages, each of said pins extendingfromV both sides of its respective said axlereceiving passage, abifurcated rocker arm having a body portion and a pair of spaced legspivotally mounted on each of said pins, the spaced legs of -each of saidrocker arms being pivotally mounted on the respective said pin onopposite sides of the respective said wheel chair axle-receivingpassage, a substantially horizontal axle-receiving passage in said bodyportion of each of said rocker arms for carrying the respective wheelaxles, and spring means operatively engageable between each of saidrocker arms and said wheel chair frame.

2. Apparatus for converting a conventional wheel chair of the typehaving a frame with a pair of spaced, substantially vertical framemembers that have substantially horizontal wheel axle-receiving passagestherethrough and a pair of substantially horizontal frame membersattached to the respective said vertical frame members into a springsupported wheel chair; including a pivot pin engageable in each of saidwheel chair axle-receiving passages, each of 'said pins extending fromboth sides of its respective said axle-receiving passage, a bifurcatedrocker arm having a body portion and a pair of spaced legs pivotallymounted on each ofv said pins, the spaced legs on each of said rockerarms being pivotally mounted on the respective said pin on oppositesides of the respective said wheel chair axle-receiving passage, asubstantially horizontal axle-receiving passage in said body portion ofeach of said rocker arms in horizontally spaced relation to therespective said pins for carrying the respective wheel axles, and springmeans operatively engageable between each of said rocker arms at a pointhorizontally spaced from the respective said pins and the respectivesaid horizontal frame members.

3. Apparatus for converting a conventional Wheel chair of the typehaving a frame with a pair of spaced, substantially vertical framemembers that have substantially horizontal wheel axle-receiving passagestherethrough and a pair of substantially horizontal frame membersattached to the respective said vertical frame members below saidaxle-receiving passages into a spring supported wheel chair; including apivot pin engageable in each of said wheel chair axle-receivingpassages, each of said pins extending from both sides of its respectivesaid axle-receiving passage, a bifurcated rocker arm having a bodyportion and a pair of spaced legs pivotally mounted on each of saidpins, the spaced legs of each of said rocker arms being pivotallymounted on the respective said pin on opposite sides of the respectivesaid wheel chair axlereceiving passage and with said body portion ofeach of said rocker arms horizontally spaced from the respective saidsubstantially vertical frame members, a substantially horizontalaxle-receiving passage in said body portion of each of said rocker armsfor carrying the respective wheel axles, and extensible spring meansoperatively engageable between said body portion of each of said rockerarms and the respective said horizontal frame members.

References Cited in the file of this patent UNITED STATES PATENTS1,577,233 Hotto Mar. 16, 1926 2,090,141 Newton Aug. 17, 1937 2,181,546Bradshaw Nov. 28, 1939 2,632,655 King et al Mar. 24, 1953 2,675,057Glass Apr. 13, 1954 FOREIGN PATENTS 626,556 Great Britain July 18, 1949640,765 Great Britain July 26, 1950 816,796 Germany Oct. 11, 1951

